Windshield
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The windshield (
Motorcycle windshields are often made of high-impact polycarbonate or acrylic plastic.
Usage
Windshields protect the vehicle's occupants from wind and flying debris such as dust, insects, and rocks, and provide an aerodynamically formed window towards the front. UV coating
On motorbikes their main function is to shield the rider from wind, though not as completely as in a car, whereas on sports and racing motorcycles the main function is reducing drag when the rider assumes the optimal aerodynamic configuration with their body in unison with the machine and does not shield the rider from wind when sitting upright.
Safety
Early windshields were made of ordinary window glass, but that could lead to serious injuries in the event of a crash. A series of crashes led up to the development of stronger windshields. The most notable example of this is the Pane vs. Ford case of 1917 that decided against Pane in that he was only injured through
Modern, glued-in windshields contribute to the vehicle's rigidity, but the main force for innovation has historically been the need to prevent injury from sharp glass fragments. Almost all nations now require windshields to stay in one piece even if broken, except if pierced by a strong force.
The urethane sealant is protected from UV in sunlight by a band of dark dots called a frit around the edge of the windshield.[3] The darkened edge transitions to the clear windshield with smaller dots to minimize thermal stress in manufacturing. The same band of darkened dots is often expanded around the rearview mirror to act as a sunshade.[4]
On a rainy day, water refraction on aircraft windshields can mislead pilots into believing that they are flying at a higher altitude than they actually are due to the horizon appearing lower than it is. This can result in undershooting the runway and become a safety hazard.[5]
Other aspects
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In many places, laws restrict the use of heavily
In aircraft windshields, an electric current is applied through a conducting layer of
The use of thermal glass prevents some navigation systems from functioning correctly, as the embedded metal blocks the satellite signal. The RF signal tends to flow along the metal wires or layer so very little radiation can pass. This can be resolved by using an external antenna. Mobile telephones can also have problems; thermal glass typically allows only 0.001 (1‰, or one per mille) of the signal to pass, whereas a concrete wall with rebars allows up to 0.100 (10%, or 100‰) of the signal to pass.
Terminology
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The term windshield is used generally throughout North America. The term windscreen is the usual term in the British Isles and Australasia for all vehicles. In the US windscreen refers to the mesh or foam placed over a microphone to minimize wind noise, while a windshield refers to the front window of a car. In the UK, the terms are reversed, although generally, the foam screen is referred to as a microphone shield, and not a windshield.
Sports or racing cars would sometimes have aero screens, which were small semi-circular or rectangular windshields. These were often mounted in pairs behind a foldable flat windshield.[6] Aero screens are usually less than 20 cm (8 inches) in height. They are known as aero screens because they only deflect the wind.[citation needed][dubious ] The twin aeroscreen setup (often called Brooklands) was popular among older sports and modern cars in vintage style.
A wiperless windshield is a windshield that uses a mechanism other than
Certification
Certification of a windshield is necessary to ensure safety. Different counties have made different set of rule that all windshield manufacturers need to comply under Motor Vehicle Acts. Some of the most know certifications are US DOT, EU ECE, Chinese CCC, South African SABS and Indian BIS standards. These certification ensures safety, reliability and quality of a product as per respective legal requirements.
Repair of stone-chip and crack damage
According to the US National Windshield Repair Association, many types of stone damage can be successfully repaired. Whether the windshield can be repaired always depends upon four factors: the size, type, depth and location of the damage.[7]
Size and depth
Repair of cracks up to 6.1 cm (2.4 inches) is within permissible limits; automobile glass with more severe damage needs to be replaced. However, this is dependent on local laws. If a crack extends to the edge of the panel then this would compromise the structural integrity of the windshield. Aircraft windshields are designed in such a way that even if a crack were to extend all the way across the panel, the structural integrity is maintained via multiple failsafe methods in both frame and the glass plies. A sacrificial outer layer that cracks rather than devitrifies is the first failsafe.
Type
Circular bullseyes, linear cracks, crack chips, dings, pits and star-shaped breaks can be repaired without removing the glass, eliminating the risk of leaking or bonding problems sometimes associated with replacement.
Location
Some damages are very difficult to repair, or cannot be repaired:
- on inside of the windshield
- deep damage on both layers of glass due to solar absorption or oxidation.
- damage over rain sensor or internal radio antenna
- complex multiple cracks
- very long cracks (i.e. over 45–60 cm or 18–24 inches long)
- contaminated cracks
- edge cracks
In cracked windshield repair, air is removed from the damaged area on the windshield with a specified vacuum injection pump. Then using the injection pump, the clear adhesive resin is injected to replace the air in the windshield crack. The resin is then cured with an ultraviolet light. When done properly, the damaged area’s strength is restored, as is 90–95% of the clarity.
Replacement
Windshields that cannot be repaired have to be replaced. Replacement of a windshield typically takes less than an hour. To ensure the vehicle is safe to drive, time values called the
Consumers may be unaware that the MDAT or SDAT time is focused on safety and not necessarily on the quality, durability, or warranty of the installation. Care must be taken not to drive the vehicle prior to the SDAT/MDAT.
Airbags deploy at speeds up to 320 km/h (200 mph; 89 m/s) and in some cases exert tremendous force on the windshield. Occupants can impact the airbag just 50 ms after initial deployment.[9] Depending on vehicle design, airbag deployment and/or occupant impact into the airbag may increase forces on the windshield, dramatically in some cases. Forces of occupants on the airbags - and hence the potential forces on the windshield - are lower for belted occupants.[10] As consequence, adhesive suppliers usually inform their customers about the level of security achieved:
1) Example: Security exceeding FMVSS 212/208 belted
2) Example: Security exceeding FMVSS 212/208 unbelted[11]
With the advent of quick-cure adhesives, mobile windshield replacements have become more prevalent. Often the temperature and humidity cannot be controlled for mobile installations. For most common glass adhesives the ideal environment is 21 °C (70 °F) and 50% humidity. Variations from the ideal curing environment can increase the time needed for a sufficiently safe bond to form. Because of the variables and difficulties involved in mobile windshield replacement, many vehicle manufacturers do not recommend this method of installations.
Disposal
See also
- Automotive head-up display
- BS 857
- Driver visibility
- Glass run channel
- List of auto parts
- Motorcycle windshield
- Windscreen wiper
- Windshield sun shade
References
- PMID 16635665. Retrieved 23 January 2013.
- ^ "Your Windshield is Not Just a "Wind-Shield" Any More". National Glass Association. Archived from the original on 2 August 2009.
- ^
Zbinden, Lyn (2014). "Chapter 7 - Ceramic Frit and Shadeband". Glass Engineering: Design Solutions for Automotive Applications. ISBN 978-0-7680-8129-9. Retrieved 9 June 2020.
- ^ Tracy, David (3 February 2017). "Here's What Those Little Dots Are On The Edges Of Your Car Windows". Jalopnik. Gawker Media. Retrieved 6 February 2017.
- ^ "Chapter 17: Aeromedical Factors". Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C ed.). Federal Aviation Administration. 2023-07-17. p. 10.
- ISBN 0854292179.
- ^ "Is Your Windshield Repairable?". Car Windshield Info. Retrieved 22 February 2014.
- ISBN 978-0080447087.
- ^ Bob Stenzel: Determining SDAT, AGRR Magazine, March/April 2012, page 29-30
- ^ Exposing Industry Shortcuts to SDAT Recommendations, Volkswagen Recall is a Reminder of Auto Glass Importance
- ^ Premium Adhesive Systems, AGRR Magazine, March/April 2012, Page 15
- ^ "Laminated Car Windscreen Recycling" (PDF). Archived from the original (PDF) on 2008-10-31.
Further reading
- How it's made. Series six, Windshields, English saddles, butter, and post clocks
- Manufacturing Processes Reference Guide: Robert H. Todd, Dell K. Allen, and Leo Alting
- Windsor, H. H. Jr., ed. (September 1933). "Shatter Proof Glass Found In Laboratory Accident". Popular Mechanics. 60 (3). Chicago, IL ISA: Popular Mechanics: 337.
External links
- UNECE Reg. 43 Safety glazing material
- BS 857:1967 Archived 2009-06-22 at the Wayback Machine Specification for safety glass for land transport
- National Glass Association
- Auto Glass Replacement Safety Standards Council